High speed, high capacity color digital printing presses have become commercially available and are seeing wider use. These systems are particularly useful for short run print jobs and situations where printing flexibility is desired. In digital color printing systems, one or more print engines print full color images by sequentially printing individual component colors of ink. One common ink color set that is widely used is Cyan (C), Magenta (M), Yellow (Y) and Black (K), referred to collectively as CMYK. These systems can print color images that have quality comparable to those produced by conventional offset presses.
To provide a greater range of colors, digital printing systems with an extended color gamut, that is, additional component ink colors, are now being used. That is, instead of four ink colors, five, six, seven and even higher numbers of component colors are being used. These additional colors can include Red (R), Green (G), Blue (B), Orange (O), Violet (V), Light Cyan (LC), Light Magenta (LM), and others. Using more component colors allows the ink colors to combine to produce final colors within a broader color space. That is, a broader range of colors can be printed on the final document, allowing more realistic and pleasing colors in photographs, images, etc.
One of the barriers to wider adoption of extended gamut color printing with digital presses is the cost to benefit ratio. Printing with, for example, 6 colors, using six separations, is more expensive than printing with four colors (e.g. CYMK), in part because of the cost of additional ink. Additionally, the use of an extended color gamut in a digital printing system tends to increase the printing time. In one system, for example, it takes approximately 0.9 seconds to print each color. Since the colors are printed sequentially on a given page, it will take almost twice as long to print a page with seven colors as one with only four colors. While the cost of six-color printing can be easily calculated, the benefit of six colors or validation that the cost is worth it on a page-by-page basis is much more difficult to determine, requiring a time-consuming manual inspection process. Without a clear and reliable method of calculating the benefit to justify the cost, wider adoption of extended gamut color printing may be hindered.